This invention relates to an assembly process and machine for press fitting a motor vehicle hub and wheel bearing together during production.
Some motor vehicle wheel hub assemblies incorporate a hub which must be press-fit into a bearing. One type of bearing unit in use today is a so-called integral bearing in which two sets of bearing elements are unified into a single assembly which is press-fit with the hub. Integral bearings provide a number of significant advantages, including the ability to prepackage and assembly the bearings at a venders facility ready for immediate installation and use by the vehicle manufacture. Integral bearing units are further protected from contamination since they are sealed prior to shipment. However, a particular concern in using these bearing units relates to their assembly with the hub. During the process of press-fitting the hub into the integral bearing, significant loads are applied which are transmitted through the rolling elements of the integral bearing. The rolling bearing elements and races are made from extremely hard materials and are designed to have a very small contact area between them. When the high press loads are imposed on the bearing unit, localized brinelling of the bearing elements at their raceway surfaces often occurs. Such brinelling causes a scoring or marking of the bearing rolling elements and races which have been found to ultimately become failure points in the bearing assembly after long use in the field. One aspect of the present invention is to overcome the problem of prior art assembly processes and machines which led to such localized brinelling. This advantage is principally achieved by causing relative rotation between the integral bearing inner and outer races during the press-fit process, which prevents the press fitting loads from being localized at specific surfaces; instead they are spread over a progressing contact area of the
The assembly process and machine of the present surfaces between the hub and bearing which are engaged by a flexible lip seal, thus preventing unlubricated surfaces from abrading the lip seal early in its service life. The process further incorporates sensors to assure correct loading of the parts before pressing and for monitoring press-on loads to determine if the correct interference fit is provided in the component.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.